Discovery of high thermoelectric performance of WS2-WSe2 nanoribbons with superlattice and Janus structures

Transition metal dichalcogenide monolayers have shown enormous potential in thermoelectric application in recent years. We now focus on the thermoelectric properties of WS 2 -WSe 2 nanoribbons with superlattice (SL) and Janus (JA) structures using first-principles calculations. The WS 2 , WSe 2 , SL, and JA nanoribbons with the ribbon width from 5 to 7 have high structural stabilities. All nanoribbon electronic structures are semiconductors and the ribbon width will modify bandgaps. It can be also observed that WS 2 , SL, and JA nanoribbons with a ribbon width of 5 have the largest carrier mobilities (up to ~500–1400 cm 2 V −1 s −1 ) and relaxation times (up to ~400–600 fs). We further calculate the electronic transport coefficients and discover that the SL and JA nanoribbons with a ribbon width of 5 exhibit the largest power factors as high as ~80 mW m −1 K −2 . Afterwards, the minimum lattice thermal conductivities of SL and JA nanoribbons are 0.53 W m −1 K −1 and 0.61 W m −1 K −1 , which are suppressed owing to the declining phonon group velocity and phonon lifetime. The maximum ZT values of SL and JA nanoribbons can reach 5.47 and 4.13. This investigation provides a solid evidence for the application of WS 2 -WSe 2 nanoribbons as promising thermoelectric materials. • All WS 2 -WSe 2 nanoribbons have stable state and semiconducting properties. • Superlattice and Janus nanoribbons have large carrier mobilities. • The smallest k ph of superlattice and Janus nanoribbons are 0.53 and 0.61 W m −1 K −1 . • The high ZT of 5.47 and 4.13 for superlattice and Janus nanoribbons are obtained.